In mission critical applications, it is important to ensure that components of a system are functioning properly and to provide quick notification to other sub-systems or components when an irregularity in functioning arises. Among many, one exemplary mission critical application is Active Driver Assistance System.
Active driver assistance systems such as radar-assisted Autonomous Emergency Braking (AEB) are expected to increase market penetration significantly in the 2015-2020 timeframe, triggered among other things by a decreased cost of ownership of mmWave automotive radar sensors operating in the 76-81 GHz frequency band.
Active safety systems such as AEB, on the other hand, need to comply with stringent levels of functional safety, for example as defined in the ISO 26262 standard. “ISO 26262 defines functional safety for automotive equipment applicable throughout the lifecycle of all automotive electronic and electrical safety-related systems. ISO 26262 is risk-based safety standard, where the risk of hazardous operational situations are qualitatively assessed and safety measures are defined to avoid or control systematic failures, and to detect or control random hardware failures, or mitigate their effects.”
In the context of a radar sensor, an ISO26262 compliant-product shall detect functional errors and flag the error condition to a central controller (from which, e.g. brake-actuators are activated, under normal operation conditions). The central controller will then disregards messages from the radar sensor until a “reset” condition takes place within the radar sensor, and the error condition is satisfactorily removed.
With this safety set-up, and in the context of an AEB system as mentioned above, undesirable and dangerous braking actions from a vehicle which would be generated as a consequence of a functional error condition within the sensor are not allowed to happen.
Looking more specifically into radar sensors and their active front-end circuitry operating at micro wave and mmWave frequencies, a number of functional tests include monitoring for over-temperature operating conditions, monitoring on the presence of local oscillator signals at the RX mixers and on the output of the power amplifiers, and so on.